Hydraulic chuck assembly

A hydraulic chuck assembly comprising:

• a housing defining an accommodation chamber which surrounds a spindle axis;
• a surrounding mount which is mounted in said accommodation chamber, and which has first and second inlets for respectively introducing therein first and second pressurized fluids, said surrounding mount having
• an inner tubular surface which defines an accommodation space, and which extends forwardly to terminate at a front peripheral end, and
• a front major wall extending radially from said front peripheral end, and having a circumferential concavity which extends rearward to form an inner surrounding surface that surrounds said inner tubular surface, and to terminate at an abutment surface;
• an annular block configured to fluid-tightly fit into said circumferential concavity, and disposed to be movable relative to said abutment surface between forward and backward positions, said annular block having a front end wall which defines inner and outer ring grooves that are disposed to be in fluid communications with said first and second inlets, respectively;
• a revolving tubular shaft including
• a smaller-diameter body segment which defines a workpiece receiving space, and which is mounted in said accommodation space to be rotatable relative to said inner tubular surface, and
• a larger-diameter head segment which is disposed forwardly from said smaller-diameter body segment to form a circumferential shoulder wall, said circumferential shoulder wall having a circumferential docking region which confronts said front end wall of said annular block, and which defines outer and inner ring ports that are configured to mate with said outer and inner ring grooves, respectively, so as to establish fluid communications therebetween, respectively, when said annular block is in the forward position, said larger-diameter head segment defining a cylindrical chamber which surrounds the spindle axis, said larger-diameter head segment having first and second passages;
• an annular piston including
• a sleeve body which is insertable in said workpiece receiving space, and
• a head body extending radially and outwardly from said sleeve body so as to partition said cylindrical chamber into front and rear sub-chambers, said front sub-chamber being in fluid communication with said inner ring port through said first passage, said rear sub-chamber being in fluid communication with said outer ring port through said second passage,
• said annular piston being disposed to be axially movable relative to said revolving tubular shaft between a releasing position, where said head body is close to said circumferential shoulder wall, and a tightening position, where said head body is remote from said circumferential shoulder wall;
• a front taper socket which has an inner taper surface that surrounds the spindle axis, and which is disposed to be moved with said annular piston;
• a front collet head mated with said inner taper surface such that, when said annular piston is displaced from the releasing position to the tightening position, said front collet head is brought into a firm engagement with a workpiece from a loose engagement therewith;
• and
• first and second valve units which are respectively disposed in said first and second passages, and which are configured such that, when the first pressurized fluid entering into said first ring port is admitted by said first valve unit to flow into said front sub-chamber, said annular piston is forced to move towards the releasing position, and such that, when the second pressurized fluid entering into said second ring port is admitted by said second valve unit to flow into said rear sub-chamber, said annular piston is forced to move towards the tightening position.